Morphology of Thyroid Follicular Cells of Methimazole-treated Rats

Impact of methimazole-induced hypothyroidism on postnatal swine

Thyroid hormones regulate metabolic rate, nutrient utilization, growth, and development. Swine are susceptible to thyroid suppression in response to disease or environmental conditions, but the physiological impact of such disruption has not been established. The objective of this study was to evaluate the impact of hypothyroidism induced with the antithyroid medication methimazole (MMI). 10 mg/kg MMI significantly decreased circulating triiodothyronine (T3) for the duration of treatment but had only a transient effect on circulating thyroxine (T4). Thyroid tissue weight was significantly increased by more than 3.5-fold in response to MMI treatment. Histologically, the eosinophilic colloid was largely absent from the thyroid follicle which displayed a disorganized columnar epithelium consistent with goiter. MMI induced hypothyroidism has no effect on growth rate over 28 days. Hepatic expression of genes associated with thyroid metabolism (DIO1, DIO2, and DIO3), lipid utilization (CD36, FASN, and ACACA), apoptosis (TP53, PERP, SIVA1, and SFN) and proliferation (CDK1, CDK2, CDK4, and CDKN1A) were unaffected by treatment. Collectively these results demonstrate that MMI induces mild systemic hypothyroidism and pronounced goiter, indicating a strong homeostatic central regulation within the hypothalamic pituitary thyroid axis. This combined with limited peripheral effects, indicates resilience to hypothyroidism in modern swine.

Enhancement of Hydrate Stability through Substitutional Defects

Cytosine monohydrate (CM) and anhydrate crystal forms reversibly interconvert under high temperatures or high humidity conditions. Here, we demonstrate through defect engineering the ability to expand the thermal stability range of CM through the targeted creation of quantifiable defects in low-level concentrations. Twelve different molecular dyes with a variety of core structures and charges were screened as potential dopants in CM. CM-dye phases prepared with Congo red (CR), Evans blue (EB), and Azocarmine G (AG) exhibited the highest inclusion levels (up to 1.1 wt %). In these doped isomorphous materials, each dye is presumed to substitute for 4-7 cytosine molecules within the low-rugosity (102) planes of the CM matrixes, thereby creating a quantifiable substitutional defect and an impediment to the cooperative molecular motions which enable the transformation to the anhydrate. Dehydration of materials with these engineered defects requires significantly higher temperatures and proceeds with slower kinetics compared to pure CM. The CM-dye phases also exhibit a reduction in the thermal expansion along key crystallographic axes and yield dehydration products with altered particle morphologies.

The influence of the lack of insulin receptor substrate 2 (IRS2) on the thyroid gland

Involvement of IRS2 in the proliferative effects of IGF-I of follicular thyroid cells has been described, but there are no evidences for in vivo participation of IRS2. This study aimed to analyse the in vivo relevance of IRS2 in the proliferation and apoptosis of thyroid cells by immunocytochemical studies for PCNA, Ki67, and active-caspase-3 in thyroid cells of IRS2 knockout (IRS2-KO) mice, jointly to TUNEL assay. Thyroid hormones were lower in IRS2-KO mice than in their wild-type (WT) counterparts. Increases in the area, perimeter and diameter of thyroid follicles of IRS2-KO mice were observed, which also showed increased proliferation rate of follicular cells and decreased percentage of apoptotic cells that was more evident in the central than in the marginal region of the gland. Sex-related differences were also found, since the follicular epithelium height was higher in male than in female mice. The percentage of proliferating cells showed significant changes in male but not in female mice, and apoptotic cells were more abundant in female than in male IRS2-KO animals, without significant differences between WT-animals. Therefore, our results suggest that IRS2 could be involved in the maintenance of thyroid cells population and in the normal physiology of the thyroid gland.

Ultrastructural Alterations in Thyrocytes of Zebrafish ( Danio rerio) after Exposure to Propylthiouracil and Perchlorate

Histopathology is a widely used approach to evaluate effects of endocrine-active chemicals in the thyroid. However, effects at an ultrastructural level have hardly been examined in fish thyroids. In the present study, zebrafish was exposed to sublethal concentrations of propylthiouracil (PTU; 0-50 mg/L) and perchlorate (PER; 0-5,000 µg/L) for 5 weeks in a modified early life-stage test. None of the treatments caused significant mortality (no observed effect concentrations for survival ≥50 mg/L [PTU] and ≥5,000 µg/L [PER]). PTU induced dose-dependent alterations in the rough endoplasmic reticulum (rER) in all exposure groups, whereas only the 2 highest PER exposure groups (500 and 5,000 µg/L) resulted in alterations of the rER. Both substances caused an increase in the numbers of lysosomes and mitochondria, with mitochondria displaying distorted cristae. Increased mitochondrial diameters were only observed in the PTU treatment. PER-exposed samples displayed an increase in apical microvilli. The highest PTU concentration (50 mg/L) showed first signs of cellular degeneration. Ultrastructural changes in zebrafish thyrocytes thus appear specific for different chemicals, most likely depending on their specific modes of action. Additional knowledge of subcellular changes in thyrocytes can help to better understand and interpret existing histological data in the future.

Resveratrol has anti-thyroid effects both in vitro and in vivo

Resveratrol is a natural polyphenol with antioxidant, anti-inflammatory, and antiproliferative properties. We have shown previously that resveratrol decreases sodium/iodide symporter expression and iodide uptake in thyrocytes, both in vitro and in vivo. In the present study, we further investigated the effects of resveratrol, with evaluation of the expression of additional thyroid-specific genes in the FRTL-5 rat thyroid cell line: thyroglobulin, thyroid peroxidase, TSH receptor, Nkx2-1, Foxe1 and Pax8. We observed decreased expression of these genes in FRTL-5 cells treated with 10 μM resveratrol. The effects of resveratrol was further evaluated in vivo using Sprague-Dawley rats treated with resveratrol 25 mg/kg body weight intraperitoneally, for 60 days. No clinical signs of hypothyroidism were seen, although the treated rats showed significant increase in thyroid size. Serum TSH and thyroid hormone levels were in the normal range, with significantly higher TSH seen in resveratrol-treated rats, compared with control rats. Histological and immunohistochemical analyses confirmed increased proliferative activity in the thyroid from resveratrol-treated rats. These data suggest that resveratrol acts as a thyroid disruptor and a goitrogen, which indicates the need for caution as a supplement and for therapeutic uses.

The differences in T and B cell subsets in thyroid of children with Graves' disease and Hashimoto's thyroiditis

BACKGROUND

The differences between Graves' disease (GD) and Hashimoto's thyroiditis (HT) suggest that changes in the subsets of T cells may have an influence on the course of these reactions.

METHODS

This study included 90 children: 30 with GD, 30 with HT, and 30 healthy children as controls. After thyroidectomy, standard histological examinations and immunohistochemical reactions were performed in paraffin specimens with monoclonal antibodies against T cell markers CD3, CD4, CD8 as well as against CD79 alpha B cells. Ultrathin sections were examined under a transmission electron microscope.

RESULTS

Autoimmune reaction in GD consisted of an increased number of CD4+ T cells (3.17±4.27%) and plasma cells (22.89±8.61%) producing thyroidstimulating hormone-receptors and stimulating thyrocytes to activity. The number of CD8+ T cells was increased in children with HT (20.54±0.68%) as compared with the controls (0.65±0.30%). The autoimmune reaction in the HT children showed antibody dependent cytotoxicity with a low number of CD4+ T cells and an increased number of CD8+ T cells in the thyroid tissue in comparison with that in the GD children and the controls. Plasma cells (31.65±9.11%) in this situation produced the antibodies involved in cytotoxic reactions against thyrocytes.

CONCLUSIONS

Graves' disease is characterized by the increased number of CD4+ T cells and CD8+ T cells. Hashimoto's thyroiditis is characterized by the low number of CD4+ T cells and increased number of CD8+ T cells. CD8+ T cells have cytotoxic properties only in Hashimoto's thyroiditis.